The science which in modern days had been called Political Economy is in reality nothing more than the investigation of the phenomena of commercial operations. It has no connexion with political economy, as understood and treated of by the great thinkers of past ages; and as long as it is allowed to pass under the same name, every word written by those thinkers — and chiefly the words of Plato, Xenophon, Cicero, and Bacon — must be either misunderstood or misapplied. The reader must not, therefore, be surprised at the care and insistence with which I have retained the literal and earliest sense of all important terms used in those papers; for a word is usually well made at the time it is first wanted; its youngest meaning has in it the full strength of its youth; subsequent senses are commonly warped or weakened; and as a misused word always is liable to involve an obscured thought, and all careful thinkers, either on this or any other subject, are sure to have used their words accurately, the first condition, in order to be able to avail ourselves of their sayings at all, is a firm definition of terms.